Much effort has been expended in recent years to find an effective and superior way of administering drugs to patients' bodies. Products such as the transdermal patch and once-a-day orally administered pills that more precisely deliver drugs have been developed. Such products are a boon to patients for they boost the effectiveness of the drugs and limit side effects by precisely controlling how quickly drugs are released in the body; by keeping drugs at a constant level and by delivering them exactly where needed.
One such development is the injection or implantation of drugs in the form of in microscopic particles or pellets at a disease site. The drugs are encapsulated in polymers or fatty compounds, such as liposomes which permit slow release of the encapsulated drug over time thereby potentially lowering the drugs toxicity.
In addition, there are times when it is desirable to deliver a biological agent that is in a non-conventional form to a disease site such as a drug in a loose particulate form, or a quantity of cells, cell clusters or cellular extracts in a biocompatible solution. A particulate biological agent can be in a granular, powdered, or microsphere form. The problem with biological agents in these forms is that they are difficult to properly deliver to a diseased tissue site.